Q&A: “How do I create a metallic car paint using V-Ray CarPaint Material?”
James Cutler gets automotive with Toby Kendal’s 3ds Max paint job question
Before V-Ray introduced its new CarPaint material, complex layer blending was the most common method for generating realistic car paint. The VRayCarPaintMtl material simplifies that process using only three layers. The paint that you’ll be creating here is called Samoa Orange Pearl.
Go to the 3ds Max preferences to enable Gamma/ LUT Correction and change Gamma to 2.2. Tick both Affect Colour Selectors and Affect Material Editor. Set Input Gamma to 2.2. Also make sure that in your V-Ray settings you’re using Linear Colour Mapping with a Gamma setting of 2.2.
Create a new VRayCarPaintMtl. The base layer is the main colour of the car paint; the colour affects both the diffuse colour and the reflection. Add a falloff map to the base colour then set the first colour to R 162, G 52, B 3. Then set the second colour to R 192, G 26, B 4. Finally set Falloff Type to Fresnel. This will create the pearl effect.
You can control the intensity of the reflection using the Base Reflection parameter – set this to 0.7. The Reflection Glossiness parameter controls how glossy the reflections will be within the base layer, so set this to 0.5.
Metallic paint has small metal flakes that can vary in colour. A similar flake colour to the base layer would create a subtle flake effect. For more elaborate results you can use a contrasting flake colour. The metal flakes will show up in brightly highlighted areas of the car’s surface, and the base layer will be more dominant in darker, less highlighted areas.
There are various controls that affect the appearance. As the flakes are reflective you can control the overall glossiness by making them more or less glossy. If set to 0, the Orientation parameter aligns all the flakes perpendicular to the surface, whereas a value of 1.0 places the flakes at a random rotation. The Density parameter controls the number of flakes on the surface, and the Scale parameter scales the entire material. By scaling you’re zooming in on the flakes and so making them appear further apart. Finally, you can adjust the size of the flakes without changing the distance between them.
The metal flakes are positioned on the surface via multiple maps. Texture maps use your computer’s memory to process the final image; by reducing the amount of memory required, the spare RAM can then be used for rendering other textures within the scene, or for different tasks entirely.
Texture maps are filtered to improve the noise level. Noise will occur because the flakes are small in size; there are two options for filtering. Simple Filtering averages all the flakes before applying the filter, and Directional Filtering groups the flakes based on their orientation before applying the filter, and will preserve the appearance of the material.
For the particular paint type you’re creating here, however, the flakes would be so small that they wouldn’t be visible, so they’re best turned off to save memory. To turn off the flakes, set Flake Density to 0.0 and Flake Scale to 0.001.
The coat layer is the final layer that will bring glossiness and depth to the material finish. Since the early days of car manufacture, the coat layer has been used to improve durability as well as appearance. In V-Ray, the diffuse colour of the coat layer can be similar or very different to the layers below. You can blend this layer to create more elaborate results. Set the coat colour to R 148, G 148, B 148. You can optionally control the glossiness and strength of the coat layer, as well as turn off trace reflections. Set Coat Strength to 0.06 and Glossiness to 0.98 so that you get some visible highlights in the coat layer.
Go to the Options panel, where you can turn off Trace Reflections Globally, make the material double-sided and adjust the number of subdivisions. Lowering the amount of subdivisions for glossy material will produce noisy results in the final image, so set the subdivisions to 22.
The Cut-Off Threshold parameter controls the distance at which a reflection is cut off. If you’re using many layered materials and maps that have varying environment overrides, you can control how a reflected or refracted ray travels through each material using the Environment Priority parameter.
Reduce RAM usage and render times
Reduce the bitmap size
Lower values reduce memory usage, but you may start to notice obvious tiling within the flakes.
Turn off Trace Reflections
By turning off Flake Trace Reflections for the three layers, only specular highlights will be produced, reducing render times.
Use Simple Filtering for the flakes
Simple Filtering uses less RAM but is less accurate because it averages the results, altering the appearance of the material.
James Cutler is a 3D digital designer who runs MintViz, which provides visualisation services, technical support and CG training
on Tuesday, August 7th, 2012 at 2:00 pm under Guides, Technique, Tutorials.
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Tags: 3ds Max, V-Ray